The present invention refers to a process and a system to realize the static error compensation on machinery in general, and particularly on numerically controlled machine tools. Examples of other types of machinery to which the present invention can be applied are measuring machines, any morphology of milling machines, electroerosion machines, plasma working machines and water-jet working machines.
The numerically controlled machine tools, after having been installed through adequate calibration operations, after a certain period of operation, show working positions that are not corresponding any more to those provided for by the control aboard the machine. These position errors are not due to a wrong operation of transducers aboard the machine, but to wrong geometries of the machine itself, assembly errors, or other reasons such as foundation settling, wear, impacts during operation, etc. In view of these disalignments between position required by control and real position reached by the tool, it should be necessary to perform machine recalibrations to bring back the machine to the xe2x80x9cidealxe2x80x9d original conditions that were present upon installation.
However, so far, these recalibrations have been realised very rarely, since for them it was necessary to use costly measuring instruments. Therefore, their use has been limited to fields in which the end product cost and the necessary precision made their use acceptable, for example the fields of aeronautics and big sea engines.
A theoretical possible alternative in the art would be using, for calibration measures, a laser interferometer, that is an inexpensive instrument. However, since for these recalibrations, it is necessary to perform a very high number of measures (in the order of thousands), for each one of which the interferometer must be used for about half an hour in order to center the mirror with the laser beam, several months would be necessary to recalibrate a machine.
Therefore, currently there are no devices or systems available in the art that allow
Some prior art examples of the above solutions are contained in the following documents:
WO-97-46925, that discloses a method for improving the accuracy of machines making use of interferometers;
U.S. Pat. No. 4,714,339, that discloses an interfetometer device;
EP-A-0 625 739, that discloses how to increase the accuracy of an apparatus for the movement of an object;
Wang S. M. et al, xe2x80x9cVolumetric Error Compensation for Multi-Axis Machinesxe2x80x9d, Emergent Innovations on Information Transfer Processing and Decision Making, Chicago,. Oct. 18-21, 1992, vol. 1, Oct. 18, 1992, pages 183-188, IEEE, that discloses a passive on-line software compensation method; and
Sugahara R., Ohsawa Y., Araki S., Yamashita H., Matsui T.: xe2x80x9cPerformance test of a laser tracker, Smart 310xe2x80x9d, Proceedings of the Fourth International Workshop on Accelerator Alignment, vol. III, Nov. 14-17 1995, pages 261-269, Tsukuba, Japan. recalibrating a machine tool allowing to realize therefor the so-called Static Error Compensation (SEC).
Object of the present invention is solving the above prior-art problems, by providing a process and a system that allow applying the Static Error Compensation (SEC) to machinery in general and to numerically controlled machine tools in particular, through an efficient, accurate and inexpensive procedure.
The above and other objects and advantages of the invention, as will appear from the following description, are obtained by a process and a system to realize the SEC as respectively claimed in claims 1 and 12. Preferred embodiments and non-trivial variations of the present invention are claimed in the dependent Claims.